tests/lib/libc/sys/t_mprotect.c

   1 /* $NetBSD: t_mprotect.c,v 1.3 2011/07/20 22:53:44 jym Exp $ */
   2
   3 /*-
   4  * Copyright (c) 2011 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Jukka Ruohonen.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31 #include <sys/cdefs.h>
  32 __RCSID("$NetBSD: t_mprotect.c,v 1.3 2011/07/20 22:53:44 jym Exp $");
  33
  34 #include <sys/param.h>
  35 #include <sys/mman.h>
  36 #include <sys/sysctl.h>
  37 #include <sys/wait.h>
  38
  39 #include <errno.h>
  40 #include <fcntl.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <unistd.h>
  44
  45 #include <atf-c.h>
  46
  47 #include "../common/exec_prot.h"
  48
  49 static long     page = 0;
  50 static int      pax_global = -1;
  51 static int      pax_enabled = -1;
  52 static char     path[] = "mmap";
  53
  54 static void     sighandler(int);
  55 static bool     paxinit(void);
  56 static bool     paxset(int, int);
  57
  58 static void
  59 sighandler(int signo)
  60 {
  61         _exit(signo);
  62 }
  63
  64 static bool
  65 paxinit(void)
  66 {
  67         size_t len = sizeof(int);
  68         int rv;
  69
  70         rv = sysctlbyname("security.pax.mprotect.global",
  71             &pax_global, &len, NULL, 0);
  72
  73         if (rv != 0)
  74                 return false;
  75
  76         rv = sysctlbyname("security.pax.mprotect.enabled",
  77             &pax_enabled, &len, NULL, 0);
  78
  79         if (rv != 0)
  80                 return false;
  81
  82         return paxset(1, 1);
  83 }
  84
  85 static bool
  86 paxset(int global, int enabled)
  87 {
  88         size_t len = sizeof(int);
  89         int rv;
  90
  91         rv = sysctlbyname("security.pax.mprotect.global",
  92             NULL, NULL, &global, len);
  93
  94         if (rv != 0)
  95                 return false;
  96
  97         rv = sysctlbyname("security.pax.mprotect.enabled",
  98             NULL, NULL, &enabled, len);
  99
 100         if (rv != 0)
 101                 return false;
 102
 103         return true;
 104 }
 105
 106
 107 ATF_TC_WITH_CLEANUP(mprotect_access);
 108 ATF_TC_HEAD(mprotect_access, tc)
 109 {
 110         atf_tc_set_md_var(tc, "descr", "Test for EACCES from mprotect(2)");
 111 }
 112
 113 ATF_TC_BODY(mprotect_access, tc)
 114 {
 115         int prot[2] = { PROT_NONE, PROT_READ };
 116         void *map;
 117         size_t i;
 118         int fd;
 119
 120         fd = open(path, O_RDONLY | O_CREAT);
 121         ATF_REQUIRE(fd >= 0);
 122
 123         /*
 124          * The call should fail with EACCES if we try to mark
 125          * a PROT_NONE or PROT_READ file/section as PROT_WRITE.
 126          */
 127         for (i = 0; i < __arraycount(prot); i++) {
 128
 129                 map = mmap(NULL, page, prot[i], MAP_SHARED, fd, 0);
 130
 131                 if (map == MAP_FAILED)
 132                         continue;
 133
 134                 errno = 0;
 135
 136                 ATF_REQUIRE(mprotect(map, page, PROT_WRITE) != 0);
 137                 ATF_REQUIRE(errno == EACCES);
 138                 ATF_REQUIRE(munmap(map, page) == 0);
 139         }
 140
 141         ATF_REQUIRE(close(fd) == 0);
 142 }
 143
 144 ATF_TC_CLEANUP(mprotect_access, tc)
 145 {
 146         (void)unlink(path);
 147 }
 148
 149 ATF_TC(mprotect_err);
 150 ATF_TC_HEAD(mprotect_err, tc)
 151 {
 152         atf_tc_set_md_var(tc, "descr", "Test error conditions of mprotect(2)");
 153 }
 154
 155 ATF_TC_BODY(mprotect_err, tc)
 156 {
 157         errno = 0;
 158
 159         ATF_REQUIRE(mprotect((char *)-1, 1, PROT_READ) != 0);
 160         ATF_REQUIRE(errno == EINVAL);
 161 }
 162
 163 ATF_TC(mprotect_exec);
 164 ATF_TC_HEAD(mprotect_exec, tc)
 165 {
 166         atf_tc_set_md_var(tc, "descr",
 167             "Test mprotect(2) executable space protections");
 168 }
 169
 170 /*
 171  * Trivial function -- should fit into a page
 172  */
 173 ATF_TC_BODY(mprotect_exec, tc)
 174 {
 175         pid_t pid;
 176         void *map;
 177         int sta, xp_support;
 178
 179         xp_support = exec_prot_support();
 180
 181         switch (xp_support) {
 182         case NOTIMPL:
 183                 atf_tc_skip(
 184                     "Execute protection callback check not implemented");
 185                 break;
 186         case NO_XP:
 187                 atf_tc_skip(
 188                     "Host does not support executable space protection");
 189                 break;
 190         case PARTIAL_XP: case PERPAGE_XP: default:
 191                 break;
 192         }
 193
 194         /*
 195          * Map a page read/write and copy a trivial assembly function inside.
 196          * We will then change the mapping rights:
 197          * - first by setting the execution right, and check that we can
 198          *   call the code found in the allocated page.
 199          * - second by removing the execution right. This should generate
 200          *   a SIGSEGV on architectures that can enforce --x permissions.
 201          */
 202
 203         map = mmap(NULL, page, PROT_WRITE|PROT_READ, MAP_ANON, -1, 0);
 204         ATF_REQUIRE(map != MAP_FAILED);
 205
 206         memcpy(map, (void *)return_one,
 207             (uintptr_t)return_one_end - (uintptr_t)return_one);
 208
 209         /* give r-x rights then call code in page */
 210         ATF_REQUIRE(mprotect(map, page, PROT_EXEC|PROT_READ) == 0);
 211         ATF_REQUIRE(((int (*)(void))map)() == 1);
 212
 213         /* remove --x right */
 214         ATF_REQUIRE(mprotect(map, page, PROT_READ) == 0);
 215
 216         pid = fork();
 217         ATF_REQUIRE(pid >= 0);
 218
 219         if (pid == 0) {
 220                 ATF_REQUIRE(signal(SIGSEGV, sighandler) != SIG_ERR);
 221                 ATF_CHECK(((int (*)(void))map)() == 1);
 222                 _exit(0);
 223         }
 224
 225         (void)wait(&sta);
 226
 227         ATF_REQUIRE(munmap(map, page) == 0);
 228
 229         ATF_REQUIRE(WIFEXITED(sta) != 0);
 230
 231         switch (xp_support) {
 232         case PARTIAL_XP:
 233                 /* Partial protection might fail; skip the test when it does */
 234                 if (WEXITSTATUS(sta) != SIGSEGV) {
 235                         atf_tc_skip("Host only supports "
 236                             "partial executable space protection");
 237                 }
 238                 break;
 239         case PERPAGE_XP: default:
 240                 /* Per-page --x protection should not fail */
 241                 ATF_REQUIRE(WEXITSTATUS(sta) == SIGSEGV);
 242                 break;
 243         }
 244 }
 245
 246 ATF_TC(mprotect_pax);
 247 ATF_TC_HEAD(mprotect_pax, tc)
 248 {
 249         atf_tc_set_md_var(tc, "descr", "PaX restrictions and mprotect(2)");
 250         atf_tc_set_md_var(tc, "require.user", "root");
 251 }
 252
 253 ATF_TC_BODY(mprotect_pax, tc)
 254 {
 255         const int prot[4] = { PROT_NONE, PROT_READ, PROT_WRITE };
 256         const char *str = NULL;
 257         void *map;
 258         size_t i;
 259         int rv;
 260
 261         if (paxinit() != true)
 262                 return;
 263
 264         /*
 265          * As noted in the original PaX documentation [1],
 266          * the following restrictions should apply:
 267          *
 268          *   (1) creating executable anonymous mappings
 269          *
 270          *   (2) creating executable/writable file mappings
 271          *
 272          *   (3) making a non-executable mapping executable
 273          *
 274          *   (4) making an executable/read-only file mapping
 275          *       writable except for performing relocations
 276          *       on an ET_DYN ELF file (non-PIC shared library)
 277          *
 278          *  The following will test only the case (3).
 279          *
 280          * [1] http://pax.grsecurity.net/docs/mprotect.txt
 281          *
 282          *     (Sun Apr 3 11:06:53 EEST 2011.)
 283          */
 284         for (i = 0; i < __arraycount(prot); i++) {
 285
 286                 map = mmap(NULL, page, prot[i], MAP_ANON, -1, 0);
 287
 288                 if (map == MAP_FAILED)
 289                         continue;
 290
 291                 rv = mprotect(map, 1, prot[i] | PROT_EXEC);
 292
 293                 (void)munmap(map, page);
 294
 295                 if (rv == 0) {
 296                         str = "non-executable mapping made executable";
 297                         goto out;
 298                 }
 299         }
 300
 301 out:
 302         if (pax_global != -1 && pax_enabled != -1)
 303                 (void)paxset(pax_global, pax_enabled);
 304
 305         if (str != NULL)
 306                 atf_tc_fail("%s", str);
 307 }
 308
 309 ATF_TC(mprotect_write);
 310 ATF_TC_HEAD(mprotect_write, tc)
 311 {
 312         atf_tc_set_md_var(tc, "descr", "Test mprotect(2) write protections");
 313 }
 314
 315 ATF_TC_BODY(mprotect_write, tc)
 316 {
 317         pid_t pid;
 318         void *map;
 319         int sta;
 320
 321         /*
 322          * Map a page read/write, change the protection
 323          * to read-only with mprotect(2), and try to write
 324          * to the page. This should generate a SIGSEGV.
 325          */
 326         map = mmap(NULL, page, PROT_WRITE|PROT_READ, MAP_ANON, -1, 0);
 327         ATF_REQUIRE(map != MAP_FAILED);
 328
 329         ATF_REQUIRE(strlcpy(map, "XXX", 3) == 3);
 330         ATF_REQUIRE(mprotect(map, page, PROT_READ) == 0);
 331
 332         pid = fork();
 333         ATF_REQUIRE(pid >= 0);
 334
 335         if (pid == 0) {
 336                 ATF_REQUIRE(signal(SIGSEGV, sighandler) != SIG_ERR);
 337                 ATF_REQUIRE(strlcpy(map, "XXX", 3) == 0);
 338         }
 339
 340         (void)wait(&sta);
 341
 342         ATF_REQUIRE(WIFEXITED(sta) != 0);
 343         ATF_REQUIRE(WEXITSTATUS(sta) == SIGSEGV);
 344         ATF_REQUIRE(munmap(map, page) == 0);
 345 }
 346
 347 ATF_TP_ADD_TCS(tp)
 348 {
 349         page = sysconf(_SC_PAGESIZE);
 350         ATF_REQUIRE(page >= 0);
 351
 352         ATF_TP_ADD_TC(tp, mprotect_access);
 353         ATF_TP_ADD_TC(tp, mprotect_err);
 354         ATF_TP_ADD_TC(tp, mprotect_exec);
 355         ATF_TP_ADD_TC(tp, mprotect_pax);
 356         ATF_TP_ADD_TC(tp, mprotect_write);
 357
 358         return atf_no_error();
 359 }